Process for treating monocyclic terpene hydrocarbons and for preparing nickel catalyst therefor



PRQCESS FOR TREATHQG MGNOCYCLI'II TER- PENE HYDRGCARB$NS AND FGR PREPAR- INS NICKEL CATALYST THEREFOR Joseph P. Bain, Robert E. Fuguitt, and Wilbur Y. Gary, .lacksonville, Fla, assiguors to The Glidden Company, Cleveland, Ohio, acorporation of Ohio No Drawing. Application June 6, 1952, Serial No. 292,204

Claims. (Cl. 263-666) This invention relates to a process for treating monocyclic terpene hydrocarbons with. an active nickel catalyst capable of edecting dehydrogenation and disproportionation reactions, and conversion of the hydrocarbons into a mixture of cyrnene and menthane.

It is already known that a mixed nickel-copper catalyst can eflect the conversion of monocyclic terpene hydrocarbons into cyrnene and menthane (U. S. Patent No. 2,211,432), but we have found that it is unnecessary to use active copper along with the active nickel. Our active nickel catalyst may be formed by the in-si'tu reduction of nickel formate accompanied with an induction period. After the active nickel catalyst has been formed, it may be used in subsequent batches without further inductive treatment.

Accordingly, it is an object of this invention to provide a novel process for couvertingmonocyclic terpene hydrocarbons into cymene in good yields by the sole use of an active nickel catalyst.

It is a further object to provide aprocess for treating nickel formate so as to prepare an active nickel catalyst capable of eifecting the conversion of monocyclic terpene hydrocarbons into cyrnene.

These and other objects will be apparent from the following description of the invention.

We have found that nickel formate yields an active catalyst capable of converting monocyclic terpene hydrocarbons into cyrnene in good yields when it is subjected to. an inductive treatment in which it is heated and agitated with a quantity of the monocyclic terpene hydrocarbons under refluxing conditions. Theinductionperiod usually varies from about 4 hours to 8 hours, although in certain cases, as with the higher boiling monocyclics gamma terpinene and terpinolene, the induction period may be as short as one hour. During this period there is little reaction as rneasured by reduction of bromine value, agitation is necessary to keep the nickel formate in suspension, and some water is liberated and is removed by a decanter. The water amounts to 20-30% by weight of the catalyst when the hydrocarbons undergoing treatment were originally dry. After the catalyst has become activated, however, disproportionation and dehydrogenation. reactions become rapid and the bromine value drops to zero within a few hours. The liberation of hydrogen during this period is generally sufficient to keep the catalyst suspended without need of mechanical agitation. After the reaction has been finished, the mass may be cooled, during which time the catalyst settles out, and. then the liquids maybe decanted or otherwise separated from the catalyst. The catalyst may then be added to a new batch of monocyclic terpene hydrocarbons and refluxed therewith. Little or, no induction period is involved with this second batch of material and only a trace of water is liberated. The disproportionation and dehydrogenation reactions begin immediately and the bromine value drops. to; zero within a few hours. In similar manner the active. catalyst may Fatented Apr. 10, 1955 n .n be employed sequentially with several further batches of material before its catalytic qualities become exhausted;

The liquid products resulting from treatment of monocyclic terpene hydrocarbons with the catalyst in the manner just described are composed mainly of cyrnene and menthane in proportions of 'about'2 to 12 parts cyrnene per part of menthane. Usually the cyrnene content of the treated mass will amount to about 70-85% of the total, although it varies with the condition of the catalyst and with the particular terpene or mixture of terpenes' being treated. The components of the treated mass may be separated and recovered etfectively by fractional distillation in conventional manners.

The monocyclic terpene hydrocarbons which are suitable for use as starting, materials for the production of cyrnene includes all of those hydrocarbons having the empirical. formula CmHre and belonging to; the para:- nrenthane series, as well as mixtures of such hydrocarbons, particularly such commercial mixtures known in the trade as dipentene, dytin, Solvenol and the like, which are composed of dipentene, dand l-lirnonene, terpinenes, phellandrenes, terpinolene and other conjugated menthadienes, such as menthadiene 2,4(8). Such materials boil between about 170 and 19.0 C. at atmospheric pressure. Amounts of cyrnene up to about 10% by weight of the total monocyclic terpene hydrocarbons may also be present in the starting material. We prefer to use freshly distilled monocyclics since the monocyclics tend to oxidize rapidly and then react sluggishly if at all.

The catalyst concentration does not appear to be: pan ticularly critical, quantities of nickel formate as low as 1% being etfective, and amounts as high as 5% exhibiting no deterrent influences on the reaction. In general we prefer to use 3-5% of catalyst.

The. catalyst should be in a powdery form and. should be maintained in suspension in the reaction mass, either by the use of suitable. mechanical agitation, or as a result of the agitation produced by the active boiling of the charge during certain phases of the treatment. During the initial treatment of the nickel formate, for its activation, water is formed in appreciable quantities, and such water should be separated from the mass as by means of a dephlegrnator. When dry, monocyclic terpenes are employed, the water so liberated amounts to 2030% by weight of the nickel formate. In subsequent runs using pre-activated catalyst, only such traces of water as may be initially present in the monocyclic terpenes are collected and separated by the dephlegmator.

As indicated above, we especially prefer to use nickel formate in preparing the active catalyst. Material of commercial purity has been found to be quite satisfactory, although variations in activity have been noticed when the products of different suppliers are compared. This ma be due to the presence of inhibitors of presently unknown nature, either in the nickel formats or in the terpenes being treated.

We have found that nickel catalysts activated in other ways than described herein, such as Raney nickel and COHTAEI'Clfll hydrogenation nickel catalysts, are either partly or wholly ineffective in reducing the unsaturation of monocyclic terpenes or mixtures thereof.

it will be understood that when preparing the active nickel catalyst in the first instance, any desired amount of nickel formate in excess of the minimum needed to treat the batch may be incorporated in the mass of terpene hydrocarbons and therein activated. We have successfully used as much as 1 part of nickel formats by Weight to 3 parts by weight of dipentene. After the catalyst has been thus activated, a portion thereof may be used in efiectiveamounts in treating subsequent. batches: of material until emausted. A further portion of'the:

r from the catalyst.

amounts larger than about 5% are employed. Large amounts of nickel formate may be activated safely in a single induction treatment since there the exothermicity is more gradual.

lt'will also be understood that in activating a given batch of catalyst, it is not necessary to carry the treatment on until the bromine value of the entire mass of liquid terpenes has been reduced substantially to zero. It is only necessary to heat the nickel formats with the liquid terpene hydrocarbons until the bromine value has been reduced more than'would be the bromine value of the mass of the same terpene hydrocarbons when similarly heated in the absence of nickel formate. Of course,

' the activating treatment may also be carried beyond this stage as far as may be desired to ensure complete activation of the catalyst, and as explained above may be continued until the bromine value of the mass has been reduced substantially to Zero.

The following examples illustrate particular embodiments of the principles of the invention:

Example 1 Three hundred ninety-one pounds of a mixture of terpenes, chiefly monocyclics, and composed of alpha terpinene; gamma terpinene; terpinolene; dipentene; menthadiene 2,4(8) and traces of related monocyclics together with a small quantity, about 5%, camphene and about 5% cymene was treated with 5% by weight of commercial nickel formate and heated at reflux. A sample withdrawn from theboiling mixture at the end of four hours showed on bromine titration that the reaction had begun since the bromine value had decreased. Between 10% and 5 0% conversion, as measured by reduction of the bromine value, hydrogen was liberated at the rate of approximately five to six cubic feet per hour. 'Hydrogen evolution gradually increased to a maximum 'rate of 190 cubic feet per hour at 82% conversion then gradually decreased to zero at the end of the run. A total of 520 cubic feet of hydrogen was evolved indicating the direct dehydrogenation of an appreciable portion of the charge. .Six-' teen hours were required to reduce the unsaturation to about 0.5% of the original value.

The charge was cooled and settled and the reaction product was decanted from the catalyst. Three hundred eighty-four pounds of fresh terpene monocyclics was added to the vessel containing the settled catalyst. On

' heating to reflux, the reaction became so vigorous that in ten minutes heating was discontinued and some cooling of the charge'by means of cooling coils was necessary to moderate the reaction. The point of maximum hydrogen evolution could not be recorded but was well in excess of 150 cubic feet per hour. After 65% conversion, the rate of hydrogen evolution decreased gradually to zero at complete conversion as measured by the absence of unsaturation. The reaction was complete in six hours.

Again the charge was cooled, settled and decanted Three hundred. fifty-eight pounds of fresh teipene monocyclics was added and the reaction proceeded smoothly with maximum hydrogen revolution of three hundred sixty cubic feet per hour. When the charge showed zero bromine value, it was cooled, settled and decanted away from the settled catalyst as before. Ten hours were required to complete the reaction.

Three hundred sixty pounds of fresh dipentene was added to the catalyst in the reaction vessel but could not be forced to react completely as it showed only 67% In other words, the whole batch of catalyst reduction in bromine value at the end of nine hours refluxing.

This charge was separated as before and the partlyconverted material held for reprocessing with fresh catalyst.

Material possessing substantially zero bromine value in the above series of experiments was combined for fractionation to rnenthane, menthane-cymene intermediates and pure cymene.

Example II 1 Samples of pure monocyclic terpenes were treated with 4% by weight nickel formate at the reflux temperature until the bromine value had dropped substantially to zero. Analyses of the crude reaction mixtures were made by infra-red spectrophotometry. During the induction period, the greenish nickel formate remains unchanged in the boiling mixture; then as the reaction begins, it rapidly turns black as metallic nickel is formed;

Percent Initial Final Total Oymene Pure Terpene r 531? .2 33 in cikude gg? reac ion 0. C. product Hours d-Limonene 179 176 9 Alpha Terp'mene" 175 176 93 13 Terplnolene 189 176 7% until the bromine value of the mass has been reduced substantially to zero, said nickel catalyst being'substantially free ofcopper and having been prepared by subjecting nickel formate to prolonged contact with monocyclic terpene hydrocarbons under refluxing conditions until activated as shown by its change in color from its original greenish color to black.

2. The process as claimed in claim 1 wherein the amount of said active catalyst is between about 1.0%

and 5% by weight of the terpene hydrocarbons being 7 treated.

3. The process as claimed in claim 1 which includes the further steps of separating the catalyst from the reaction mass, and fractionally distilling the liquid components of the treated mass to recover cymene and menthane therefrom.

4. The process as claimed in claim 1 which includes the further step of separating the catalyst from the reac tion mass-and subsequently using it to treatadditional batches of monocyclic terpen e hydrocarbons by the process of claim l until the activity of the catalyst has been exhausted.

5. The process of preparing an active nickel catalyst which is capable of dehydrogenating and disproportionating monocyclic terpeue hydrocarbons substantially completely to cymcue and menthanes when heated with said hydrocarbons in liquid phase in the absence of copper, said process comprising the step of subjecting nickel fornate to prolonged contact with monocyclic terpene hydrocarbons under reflux conditions until the bromine value of said hydrocarbons has been reduced substantially more than would be the bromine value of said terpene hy- 3 drocarbons when similarly heated in the absence of nickel FOREIGN PATENTS formate, and until the color of the catalyst has hang 92,434 Sweden Jung 3, 1938 to black from its original gresnish color. OTHER REFERENCES References Cited in thefile of this patent 5 Treibe Berichte, vol. 68B, pages 1041-1049 (1935). UNITED STATES PATENTS Abstracted in Chem. Abstracts, vol. 29, page 5435 (1935).

2,052,917 Bcrgstrom Sept. 1, 1936 2,211,432 Palmer or al. Aug. 13, 1940 

1. THE PROCESS OF TREATING MONOCYCLIC TERPENE HYDROCARBONS, WHICH COMPRISES: HEATING SAID HYDROCARBONS TO REACTION TEMPERATURES IN THE LIQUID PHASE IN THE PRESENCE OF AN EFFECTIVE AMOUNT OF AN ACTIVE NICKEL CATALYST UNTIL THE BROMINE VALUE OF THE MASS HAS BEEN REDUCED SUBSTANTIALLY TO ZERO, SAID NICKEL CATALYST BEING SUBSTANTIALLY FREE OF COPPER AND HAVING BEEN PREPARED BY SUBJECTING NICKEL FORMATE TO PROLONGED CONTACT WITH MONOCYCLIC TERPENE HYDROCARBONS UNDER REFLUXING CONDITIONS ORIGINAL GREENISH COLOR TO BLACK. 